docs: def parse_blob_snapshot_parameter(url):
      # type: (str) -> str
      """Retrieves the blob snapshot parameter from a url
      :param url str: blob url
      :rtype: str
      :return: snapshot parameter
      """
      if blob_is_snapshot(url):
          tmp = url.split('?snapshot=')
          if len(tmp) == 2:
              return tmp[0], tmp[1]
      return None